The invention belongs to the technical field of
ceramic material preparation, and provides a high-thermal-
conductivity silicon nitride ceramic substrate and a preparation method thereof. According to the method, a high-entropy
oxide sintering aid is prepared through a
coprecipitation calcination method,
titanium hybrid polycarbosilane is chemically synthesized to serve as a functional aid, and meanwhile
silicon nitride powder is subjected to
surface coating modification; the preparation method comprises the following steps: uniformly mixing modified
silicon nitride powder with the two assistants, carrying out
tape casting to obtain a biscuit, carrying out multi-stage air pressure
sintering on the biscuit, regulating and controlling
atmosphere, pressure and temperature in a
sintering procedure, completing low-
temperature treatment,
vacuum sintering, high-pressure densification and high-temperature and high-pressure sintering step by step, and carrying out specific annealing treatment in a cooling stage to obtain the
silicon nitride ceramic. According to the invention, by utilizing the synergistic effect of the compound additive and a precise sintering schedule, the growth of
silicon nitride grains is effectively promoted, and the
grain boundary phase is optimized, so that the prepared
silicon nitride ceramic substrate is highly compact in structure and pure in
grain boundary, and excellent heat-conducting property is realized.